Narrative:

I was instructing a student in small aircraft X. On left downwind for runway 29L we were followed by an small aircraft Y. The tower instructed small aircraft Y to land on runway 29R. We were cleared to touch and go on the 29L runway. As we turned final for 29L, we spotted small aircraft Y turning final for 29L also, small aircraft Y was well in front of us and there was no conflict and no need to take evasive action. The 2 planes didn't get closer than 1/4 mi. As our aircraft leveled out on final for 29L, the local controller notified small aircraft Y of his mistake. The controller also notified us of the situation, that the small aircraft Y had turned final for 29L, also. I replied that we had small aircraft Y in sight and that we would maintain sep. When I released the microphone button, I heard the small aircraft Y pilot in mid-sentence. He had begun transmitting before I had stopped, probably because he was anxious about the situation. The small aircraft Y pilot side-stepped to the left of the runway and went around. Our approach and touch and go was uneventful. However, we may have been a factor in this incident. My student had extended the downwind leg, hoping for a better approach and more time to get set up for landing. As a result, I suspect that the small aircraft Y pilot thought we were going for the other runway and assumed his clearance was for 29L, which it was not. It was a mistake on his part, and he should have asked the controller for clearance verification instead of assuming we were going to the other runway and he was cleared to 29L.

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Original NASA ASRS Text

Title: TRAINING SMA LINES UP WITH WRONG RWY IN FRONT OF REPORTER'S TRAINING SMA AT BJC.

Narrative: I WAS INSTRUCTING A STUDENT IN SMA X. ON LEFT DOWNWIND FOR RWY 29L WE WERE FOLLOWED BY AN SMA Y. THE TWR INSTRUCTED SMA Y TO LAND ON RWY 29R. WE WERE CLRED TO TOUCH AND GO ON THE 29L RWY. AS WE TURNED FINAL FOR 29L, WE SPOTTED SMA Y TURNING FINAL FOR 29L ALSO, SMA Y WAS WELL IN FRONT OF US AND THERE WAS NO CONFLICT AND NO NEED TO TAKE EVASIVE ACTION. THE 2 PLANES DIDN'T GET CLOSER THAN 1/4 MI. AS OUR ACFT LEVELED OUT ON FINAL FOR 29L, THE LCL CTLR NOTIFIED SMA Y OF HIS MISTAKE. THE CTLR ALSO NOTIFIED US OF THE SITUATION, THAT THE SMA Y HAD TURNED FINAL FOR 29L, ALSO. I REPLIED THAT WE HAD SMA Y IN SIGHT AND THAT WE WOULD MAINTAIN SEP. WHEN I RELEASED THE MIC BUTTON, I HEARD THE SMA Y PLT IN MID-SENTENCE. HE HAD BEGUN XMITTING BEFORE I HAD STOPPED, PROBABLY BECAUSE HE WAS ANXIOUS ABOUT THE SITUATION. THE SMA Y PLT SIDE-STEPPED TO THE LEFT OF THE RWY AND WENT AROUND. OUR APCH AND TOUCH AND GO WAS UNEVENTFUL. HOWEVER, WE MAY HAVE BEEN A FACTOR IN THIS INCIDENT. MY STUDENT HAD EXTENDED THE DOWNWIND LEG, HOPING FOR A BETTER APCH AND MORE TIME TO GET SET UP FOR LNDG. AS A RESULT, I SUSPECT THAT THE SMA Y PLT THOUGHT WE WERE GOING FOR THE OTHER RWY AND ASSUMED HIS CLRNC WAS FOR 29L, WHICH IT WAS NOT. IT WAS A MISTAKE ON HIS PART, AND HE SHOULD HAVE ASKED THE CTLR FOR CLRNC VERIFICATION INSTEAD OF ASSUMING WE WERE GOING TO THE OTHER RWY AND HE WAS CLRED TO 29L.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.